• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.83-90
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• 2011

A need still exists that the unsaturated condition is to be considered when evaluating the infiltration and drainage capacity for compacted geomaterials in road foundation or embankments. For this reason, numerical analysis were used to analyze the time-dependent unsaturated infiltration and drainage condition depending on various geomaterial types. Therefore, laboratory data from the soil-water characteristic curve tests on geomaterials were adopted from previous studies. In addition, the unsaturated permeability was estimated using SWCC. Then the infiltration and drainage performance of unsaturated compacted soils were evaluated under various conditions based on the proposed method. The results demonstrated that the effect of initial suction and SWCC path on each material could be substantial and the proper application on analysis is very important to enhance the prediction on each capacity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.73-82
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• 2011

Generally, an unsaturated condition was not considered to predict the long-term strength and drainage behaviors on compacted road foundations. However, it is logical way to consider the unsaturated condition and hysteresis behavior on road foundations like subbase and subgrade. For more quantitative analysis, rational experimental approach requires proper laboratory tool and material model, and hydraulic properties of pavement geomaterials under unsaturated conditions. In this study, therefore, laboratory data from the soil-water characteristic curve tests were used to predict suction and unsaturated permeability on pavement foundations and the results were analyzed based on the nonlinear fitting model considered. In addition to that, the unsaturated moisture capacity of each material is discussed.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.1-8
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• 2014

Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.191-194
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• 2003

The purpose of this paper was to derive soil-water characteristic curve equation for unsaturated soil. To this end, a series of suction measured test was conducted on the selected 4 kinds of soil which is located in Korea, used the modified pressure plate apparatus. From the test results, it was proved that characteristic curve changes according to grain size distribution, size of void and fine grained soil contents. Residual degree of saturation(Sr) was decreased with void ratio and changed with fine grained soil contents, parameter ${\lambda}$ and hr was increased with void ratio. Soil-water characteristic curve equation based on the test result was suggested by void ratio or grain size distribution.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1996.11a
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• pp.50-53
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• 1996

This paper reports the experimental results for the determination of the overall partition coefficient of VOCs in unsaturated soil, A chromatographic method was used for the determination of gaseous partition coefficients to natural soil under various water content conditions. The equilibrium vapor pressure of water over saturated salt solution was used to fix the relative humidity of the air and control the water content of the soil systems. The transport behavior was studied for dichloromethane, trichloroethane and dichlorobenzene pollutants, with log octanol-water partition coefficients(log $K_{ow}$ ) which range from 1.25 to 3.39, or water to soil partitioning which varies by 135 times; water solubility constants which vary by 3 times; and vapor pressures which range from 1 to 362 torr. Water content of the soil had a pronounced effect on the effective partition coefficient(between gas and soil + water stationary phase) as well as on the effective dispersion coefficient.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.873-881
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• 2004

A serious of EK remediation tests on contaminated soil are performed under unsaturated conditions and analyzed for electrical potential, water content, pH and so on. The results indicated that electrical potential and pH distributions in the sample are dependent on the amount and inward/outward flow of hydrogen ion. Specially, for the closed system the water content is largely decreased with the flow of hydrogen. The maximum electrical conductivity is measured at the catholyte of CEM(Sealing) test and directly related to the remedial efficiency. Although pHs in the region near to the anode are similarly developed, the different concentration of lead is measured with the electrical gradient contrary to the lead concentration dependent on pH within the sample.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.890-896
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• 2004

This study is intended as an investigation of the EK remediation characteristics of natural soil with treatment time under unsaturated conditions. EK tests are performed under the voltage gradient of 1V/cm, the degree of saturation of 82.8%, and the installing of cation exchange membrane. It was found from the results that the acid front is initially transported at 0.75cm/day and then continuously degreased until the transport velocity of the acid front is balanced to the velocity of the base front. The residual lead concentration indicated the maximum value at the treatment time of lOdays, then the increasing of treatment time largely decreases the concentration within the sample though electromigration than electroosmosis.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.361-366
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• 2005

Since most soils exist above the ground water table, negative pore pressure exist in unsaturated soils. Negative pore water pressure in unsaturated soil affects the soil structure and degree of saturation and it is important for accurate evaluation of unsaturate flow and behavior. This negative pore pressure is called a matric suction which causes an increased shear strength. Therefore, it is required that the effect of increase in the shear strength should be included in a geotechnical analysis. From the test result, the influence of net confining pressure and matric suction on the shear strength was analyzed and strength parameter was increased with matric suction increase and a unliner relationship was found to relate matric suction and shear strength.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.216-220
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• 1998

Experimental studies were carried out to investigate water diffusion in unsaturated compacted bentonite for a landfill of hazardous wastes. Water content distributions were measured and water diffusion coefficients were determined when the dry densities of compacted bentonite were in the range of 1.4 - 1.8 g/㎤. Resaturation times were also calculated to analyze the ability of the compacted bentonite to retard water movement. The results obtained were as follows: Diffusion model described properly the water migration in unsaturated compacted bentonite. Water diffusion coefficients ranged from 4.30$\times$10$^{-6}$ $\textrm{cm}^2$/sec to 1.93$\times$10$^{-6}$ $\textrm{cm}^2$/sec, and decreased with increasing the dry density. The dry density of compacted bentonite was found to be an important factor to control the resaturation time by water. This study suggests that the domestic compacted bentonite should be a good barrier material against water movement in a landfill of hazardous wastes.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.105-110
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• 2008

The behaviour of an unsaturated soil was analyzed by performing $K_0$ consolidated triaxial tests. Unsaturated triaxial tests were performed with matric suctions for weathered soils and could catch stress paths under consolidation and stress-strain relationships under shear. As a result, both isotropic and $K_0$ conditions had similar shear strength envelopes in the same matric suction. Especially, strength parameters could obtain by stress variables based on critical state theory reasonably which was better than those by Mohr circles at failure.